1. Field of the Invention
The present invention relates in general to a lubrication for a horizontal type rotary compressor and, more particularly, to a lubricating device for the horizontal type rotary compressor.
2. Description of the Prior Art
With reference to FIGS. 1A and 1B, there is shown a construction of a conventional lubricating device for a horizontal type rotary compressor. The compressor has an eccentric rotating shaft 4 which is axially positioned in a shell 1 constituting a horizontal compressor casing. The eccentric shaft 4 is received in a cylindrical cavity of a compression cylinder 2, defining a compression chamber C therein, and provided with a roller 3 thereabout. An outer surface of this roller 3 comes into contact with an inner surface of the compression cylinder 2. The cylinder 2 is coupled at its both sides to a main bearing 5 and a sub bearing 6, respectively, which support the shaft 4 at opposed sides of the cylinder 2 and define the compression chamber C in cooperation with the inner surface of the cylinder 2. The compressor is provided with the lubricating device for lubrication of its friction parts. The lubricating device comprises a vane slot 2a which is provided in a lower section of the cylinder 2 such that it communicates with the compression chamber C of the cylinder 2. This vane slot 2a movably receives a spring-biased vane 7 which is biased upwards by a compression coil spring 8 provided under the vane 7. The distal end of the vane 7 comes into close contact with the outer surface of the roller 3, so that when the roller 3 of the shaft 4 is eccentrically rotated in the cavity of the cylinder 2 in accordance with the rotation of the shaft 4, the spring-biased vane 7 elastically advances and retracts. Otherwise stated, this vane 7 vertically reciprocates in the vane slot 2a. An oil pumping chamber 9 is provided in the cylinder 2 under the vane slot 2a. The pumping chamber 9 is defined by the lower end of the reciprocating vane 7, and the main and sub bearings 5 and 6 coupled to both sides of the compression cylinder 2.
The oil pumping chamber 9 is provided with an oil inlet hydraulic diode 10 formed in the sub bearing 6 and with an oil outlet hydraulic diode 11 formed in the main bearing 5. Owing to the vertical reciprocation of the vane 7, the lubrication oil "o" charged in the lower section of the shell 1 flows in the oil pumping chamber 9 through the oil inlet diode 10 and, thereafter, is delivered to an oil conduit 13 of the rotating shaft 4 through the oil outlet diode 11 in order to be supplied to the friction parts of the compressor. The communication of the oil outlet diode 11 with the oil conduit 13 of the rotating shaft 4 is achieved by an oil feed pipe 12 connected therebetween.
The oil conduit 13 of the rotating shaft 4 is in turn provided with a plurality of lubricating slots 13a which vertically extend from the conduit 13 and through which the oil conduit 13 communicates with friction parts of the compressor.
As shown in FIG. 1A, each of the oil inlet and outlet diodes 10 and 11 has a nozzle shape such that the sectional areas at both ends thereof are different from each other. That is, the nozzle shape of the inlet diode 10 is concentrated toward the pumping chamber 9 while the nozzle shape of the outlet diode 10 is concentrated toward the outside of the pumping chamber 9. Due to the shapes of the diodes 10 and 11, the flow resistance of the diodes 10 and 11 is very small when the lubrication oil flows leftwards as shown at the arrows of FIG. 1A. However, the flow resistance of the diodes 10 and 11 is remarkably increased when the lubrication oil flows rightwards, so that very small amount of oil flows through the diodes 10 and 11 even though the pressure difference between the inside and the outside of the pumping chamber 9 in the rightward flowing of the oil remains the same as that of the leftward flowing of the oil. In this regard, the diodes 10 and 11 result in a problem that when it is require to flow the lubrication oil in opposed directions, the desired smooth flow of the lubrication oil through them is achieved only in one direction, that is, the leftward direction.
In operation of the above lubricating device, the vertical elastic reciprocation of the vane 7 caused by eccentric rotation of the shaft 4 causes the lubrication oil "o" in the shell 1 to flow through the inlet diode 10, the pumping chamber 9, the outlet diode 11 and the oil feed pipe 12, thus to be introduced to the oil conduit 13 of the shaft 4. At this time, the aforementioned flowing of the lubrication oil is achieved by change of the inner volume of the pumping chamber 9 as well as by an oil pressure difference between the inside of the shell 1, the pumping chamber 9 and the oil feed pipe 12 generated by the vertical reciprocation of the vane 7.
For example, when the vane 7 moves upwards, the volume occupied by the vane 7 in the pumping chamber 9 is reduced and this causes generation of negative pressure in the pumping chamber 9. The lubrication oil in the shell 1 is thus sucked into the pumping chamber 9 through the oil inlet diode 10. At this time, the lubrication oil intending to reversely flow from the feed pipe 12 to the pumping chamber 9 is limited in its amount to be very small since the oil outlet diode 11 restricts the reverse flow of the oil due to its shape. Thereafter, the vane 7 moves downwards as a result of the rotation of the shaft 4, so that the inner volume of the pumping chamber 9 is reduced and, as a result, the oil in the chamber 9 is compressed. The lubrication oil under pressure is thus supplied to the rotating shaft 4 through the oil outlet diode 11 and the oil feed pipe 12.
During the oil supply from the pumping chamber 9 to the shaft 4, the lubrication oil intending to reversely flow from the pumping chamber 9 to the inside of the shell 1 is limited in its amount to be very small since the oil inlet diode 10 restricts the reverse flow of the oil due to its shape. A predetermined amount of lubrication oil, that is, the difference between the amount of the lubrication oil flowing out through the oil outlet diode 11 and the amount of the lubrication oil flowing out through the oil inlet diode 10, is supplied to the oil conduit 13 of the shaft 4 through the oil feed pipe 12 and in turn to the friction parts of the compressor through the lubricating slots 13a.
However, the conventional lubricating device for the horizontal type rotary compressor should have the main and sub bearing 5 and 6 which are relatively larger in their sizes since they support the rotating shaft 4 at opposed sides of the compression cylinder 2 and also cover the opposed sides of the vane 7 in order to form the side walls of the pumping chamber 9. Due to the larger size of the bearings 5 and 6, the conventional lubricating device introduces a problem that it increases the size and the cost of the compressor.
The lubricating device should have the compression coil spring 8 in the oil pumping chamber 9 for biasing the vane 7 upwards. Hence, when the lubricating device is adapted to a compressor having a longer distance between upper and bottom dead points of the vane 7, that is, having a larger eccentricity of the rotating shaft 4, the compression coil spring 8 is inevitably limited in its minimum height during its compression. Furthermore, when the lubrication oil in the pumping chamber 9 is compressed, the compressed coil spring 8 is such reduced in the gaps between its coils that there is generated a flow resistance in the pumping chamber 9 by the presence of the compressed coil spring 8, thus to prevent a desired smooth flowing of the lubrication oil in the chamber 9.
In addition, the lubricating device generates bubbles in the lubrication oil in the shell 1 during its initial operation and introduces the bubbles together with the lubrication oil to the oil conduit 13 of the rotating shaft 4, thus to result in a bad lubrication.